Traditionally, fabric conditioning has been carried out either during the rinsing step of a fabric washing and rinsing process or during tumble drying of the fabric. Typically, rinse conditioning is accomplished by adding a liquid dispersion of a rinse conditioning agent to the rinse liquor. The liquid dispersion was traditionally distributed and made available to consumers as a ready to use aqueous dispersion. More recently, concern for the environment and consumer convenience has led to the sale of concentrated aqueous dispersions which are either used in smaller amounts or are mixed with water to form a dilute composition before use.
In EP 234082 it has been proposed to supply rinse conditioner as a solid block. This approach requires the use of a special restraint for the block and may also require the modification of the washing machine to enable the block to be dissolved and dispensed by a spray system. Various proposals have been made to supply fabric softener in granular or powdered form.
EP 111074 discloses a powdered rinse conditioner based on a silica carrier for the softening agent. A disadvantage of using a carrier such as silica is that it can cause bulking of the product and appears to serve no function beyond making the powder compatible with other ingredients that may be contained in a washing powder.
WO 92/18593 describes a granular fabric softening composition comprising a nonionic fabric softener and a single long alkyl chain cationic material. The specification teaches that effective cationic softening compositions when used in granular form exhibit poor dispersion properties and so, despite the obvious environmental and transport saving advantages of selling a water free powdered rinse conditioner, manufacturers have not done so.
EP-B1-0568297 discloses a powdered rinse conditioner comprising a water insoluble cationic active and a nonionic dispersing agent.
It is known that solid fabric conditioners can be formed by combining quaternary ammonium compounds with a water soluble carrier such as urea.
U.S. Pat. No. 5,259,964 (Colgate-Palmolive) discloses a free flowing spray-dried rinse conditioner. U.S. Pat. No. 4,427,558 (Unilever) discloses a method of preparing fabric softening particles comprising a cationic fabric conditioning material, urea and a salt of a fatty acid.
A problem with powdered rinse conditioners is that, once dissolved/dispersed in the rinse liquor, it is difficult to achieve good deposition of the softening agent onto the fabric being treated.
Deposition aids have been proposed for depositing clay softeners. For example, WO-Al-00/60039 (Proctor and Gamble) discloses a solid rinse conditioner comprising clay, surfactant, a solid carrier and a flocculating agent which aids deposition of the clay. The preferred flocculating agent is an organic polymer such as polyethylene oxide.
EP-A-0107479 (Unilever) discloses a liquid or granular rinse conditioner comprising a nonionic conditioner (such as sorbitan monostearate) and aluminium chloro-hydrate which acts as a deposition aid for the nonionic conditioner.
EP-A-0267999 (Unilever) discloses a liquid or powder rinse conditioner comprising a non-cationic softener and a nonionic cellulose ether derivative as a deposition aid for the softener.
JP 06306769 (Kao) discloses a solid fabric softener comprising a tertiary amine, a quaternary ammonium salt and urea or a water soluble inorganic salt.
JP 62057639 (Lion) discloses the production of cationic surfactant granules in which a dialkyl quaternary ammonium powder is granulated with an alkali metal chloride or an alkaline earth metal chloride. The chloride is present to improve softness.
JP 02182972 (Kao) discloses a solid softening agent comprising a dialkyl quaternary ammonium salt, a monoalkyl quaternary ammonium salt and urea or a urea derivative. The composition may also contain a water soluble inorganic salt such as sodium chloride, sodium sulphate, magnesium sulphate and potassium nitrate.
Surprisingly, it has now been found that a solid rinse conditioning composition comprising a cationic softening agent and a carrier, such as urea, provides significantly improved deposition of the cationic softening agent onto fabrics when citric acid or a salt of citric acid is present in the formulation. Furthermore, it is found that greater perfume strength is imparted to dried fabrics which have been treated with such compositions.
Salts of citric acid have been disclosed in solid detergent formulations. See, for instance, WO 94/04643 (Colgate Palmolive) and U.S. Pat. No. 6,110,886 (Sunburst).
U.S. Pat. No. 4,814,095 (Henkel) discloses an afterwash textile treatment preparation based on a layer silicate and comprising citric acid, a zeolite and urea. The citric acid is used as a neutralising and disintegrating agent. Example 5 discloses a composition comprising a single chain quaternary ammonium material (tetradecyl trimethyl ammonium bromide). This is not a fabric softening agent.
GB-A-2348435 discloses, in example D, a composition comprising QEA, QAS, citric acid, perfume, sodium sulphate and sodium carbonate. QEA and QAS appear to be highly soluble materials and would thus be ineffective as fabric softening agents. Suitable softening components are described on page 3 and include a surfactant component selected from anionic or nonionic surfactants.
None of the prior art has identified that, in a fabric conditioning composition comprising a cationic softening agent and a carrier such as urea, citric acid or a salt of citric acid provides excellent deposition of the softening agent onto the fabrics being treated.
In addition, there is nothing in the prior art which suggests that improved perfume strength on dried fabrics can be achieved using such compositions.